US 3731726 A
A method of casting jewellery of bimetallic construction, in which a first metallic part is embedded in a wax model of the second part and the combined metal part and wax model is then immersed in liquid investment, which investment is then allowed to harden in the conventional manner. The investment is then subjected to moderate heating, sufficient to melt the wax and cause the wax to run out of the cavities in the investment, but being insufficient to affect the finish on the metallic first part within the investment. A wax solvent then removes the last traces of wax and the investment is then placed in an oven and heated for an extended period at a moderate temperature, again being controlled so as to be insufficient to in any way affect the finish or form of the first metal part which remains trapped within the investment. The second metal in a molten state, is then poured into the cavities in the investment in such a way as to ensure rapid and complete filling of the cavities. The molten second metal then envelops portions of the first metal part exposed within the cavity, and after hardening, the first and second metal parts are securely fastened together without any requirement for further soldering or other fastening.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 3,731,726 Eberle 1 May 8, 1973  METHOD OF CASTING BIMETALLIC tion, in which a first metallic part is embedded in a JEWELLERY lnventor: Otto Eugen Eberle, 421 Guildway Parkway. West Hill, Ontario, Canada Primary ExaminerRobert D. Baldwin AltorneyGeorge A. Rolston  ABSTRACT A method of casting jewellery of bimetallic construcwax model of the second part and the combined metal part and wax model is then immersed in liquid investment, which investment is then allowed to harden in the conventional manner. The investment is then subjected to moderate heating, sufficient to melt the wax and cause the wax to run out of the cavities in the investment, but being insufficient to affect the finish on the metallic first part within the investment. A wax solvent then removes the last traces of wax and the investment is then placed in an oven and heated for an extended period at a moderate temperature, again being controlled so as to be insufiicient to in any way affect the finish or form of the first metal part which 9 Claims, 10 Drawing Figures Patented May 8, 1973 3,731,726
2 Sheets-Sheet l INVENTOR.
OTTO E. EBERLE BY: I
Patented May 8, 1973 2 Sheets-Sheet 2 FIG. 10
Inventor P 3] F A V HA 4 m A m r Z v. M? V1 6) 3 M w. m 5 4 OTTO .E. EBERLE by: gwya METHOD OF CASTING BIMETALLIC JEWELLERY The present invention relates to a method of casting bimetallic jewellery, the two metals being usually yellow gold and white gold, although obviously other precious metals such as are used in jewellery construction can also be cast according to the same general method.
BACKGROUND OF THE IN VENTIO N Jewellery such as rings and the like has been manufactured for many hundreds of years by first of all casting the metallic part or parts by what is known as the lost wax" process. In this process, a wax model of the jewellery item or ring is formed, usually by casting the wax in a rubber mould. A group of the so-called waxes are then mounted together on a tree-like device or ring, depending upon the particular technique used, and the group of waxes is then placed within a steel flask or container which is then filled with liquid plaster or other so-called investment. The flask containing the hardened investment and waxes is then placed in an oven for an extended period of time at an elevated temperature so as to melt the wax which then runs out of the investment, leaving cavities in the investment of a shape and size corresponding to the form of the metallic portions of the rings and the like. Gold or other precious metal is then poured into the cavities formed in the investment, usually under centrifugal force, afterwhich the gold is allowed to harden. The investment is then broken away from the hardened gold rings which are then polished and set with stones and the like.
In order to get a high finish on the gold castings, and in order to ensure the conformity of the gold castings with the cavities within the investment, great pains must be taken according to this method, to remove every particle of wax. This is usually achieved by mounting the flasks of investment upside down in the oven so that as soon as the same becomes warm the wax will run out. As the temperature of the oven continues to rise and the investment is heated completely through to a very high temperature not less than l,300 F and every last particle of wax is converted into carbon which is burned up at l,300 F and the cavities are thereby left clean.
This process has served the jewellery industry very well for many hundreds of years.
However, as fashions in jewellery have changed, it becomes increasingly desirable to manufacture jewellery items such as rings and the like in which the setting carrying the stone is made of white gold, and in which the band is made of yellow gold. This is particularly desirable since the white gold tends to provide a better and more flattering setting for the stones than does yellow gold. whereas yellow gold is regarded as a more traditional material for the band. Similarly, it may be desirable, in the interest of the economy of manufacture, to manufacture rings even when they are made all of one colour of metal, in two parts. According to this technique, a variety of different jewel setting pieces may be manufactured in a very wide variety of differing styles, and these may be manufactured for inventory. As and when orders are received for specific styles, then the particular style setting may be removed from storage, and a suitable band formed afterwhich the two parts may be assembled together and sold to the customer. In this way, the employment of the staff in the manufacturing concern may be extended virtually over the entire working year, even though orders for jewellery are customarily received only in about 3 or 4 months of the year. During the slack months, the staff can manufacture settings for inventory with low material costs, and during the peak months virtually the same staff can be engaged full time simply in manufacturing bands for assembling with the various settings which have already been made and stored.
In either case, either when using two different colours of metal, or when using two parts of the same colour, traditional manufacturing techniques have required that the setting and the band should be formed so that a portion of the setting was designed to interfit crudely into a recess in the band, and the two were then fastened together by means such as hard solder. The application of solder to a piece of jewellery such as this requires very great skill and practice. In fact, it is almost impossible even for the most highly skilled technician to apply solder in such a location in such a way that it is invisible to the naked eye. In many cases, traces of solder are left which must then be removed by further polishing, involving still further processing time. A further disadvantage is the fact that the soldered joint is not always completely satisfactory. If the ringwhen delivered to the customer is found to require adjustment in the size of the band, then when the band is bent or contracted to a smaller size, the soldered joint frequently was broken.
These various factors therefore tended to greatly increase the cost of manufacture of rings and other jewellery items involving the junction of two metallic parts, whether of the same colour of metal or a different metal. As a result, the true flexibility and economy of manufacture employing two part construction, has never been fully realized.
BRIEF SUMMARY OF THE INVENTION The invention therefore seeks to provide a method of casting jewellery of bimetallic construction, in which a first metallic part is cast according to the conventional lost wax method or made by any other method such as die stamping. The first portion, which will usually be the setting is then embedded into a wax model of the second portion, usually the band. The combined metal setting, and wax model of the band are then assembled into a group of waxes according to known techniques, and these waxes are then placed in an investment flask which is then filled with liquid investment, which investment is then allowed to harden in the conventional manner. The flask is then subjected to controlled moderate temperature heating, sufficient to melt the wax and cause the wax to run out of the cavities in the investment, but being insufficient to affect the finish on the metallic first portions which still remain within the investment. The flask is then immersed in a wax solvent which removes the last traces of wax from within the cavities, and the flask is then removed and allowed to dry. The flask is then placed in an oven and heated for an extended period at a moderate temperature, again being controlled so as to be insufficient to in any way affect the finish or form of the first metal portions which remain trapped within the investment. After thorough heating, the second metal, in a molten state, is then poured into the cavities in the investment, while at the same time air is withdrawn from the cavities under vacuum so as to ensure rapid and complete filling of the cavities. The molten second metal will then flow around and envelop portions of the first metallic part exposed within the cavity, and after hardening, the first and second metal parts will be found to be securely fastened together without any requirement for further soldering or other fastening.
Preferably, by the practice and method according to the invention, the actual casting step is carried out with the aidof the application of a vacuum at both ends of the flask, the investment material in its dry hardened state being somewhat porous and allowing the passage of limited quantities of air therethrough, and the application of the vacuum thereby ensuring that any residual air within the cavities is withdrawn through the investment material as the molten metal enters the cavities.
Further in accordance with the invention, the flask is preferably subjected to high speed rotation whereby to ensure entry of the molten metal into the cavities under centrifugal force.
Further and related objectives and advantages will become apparent from the following description of a preferred embodiment of the invention which is given here by way of example only and with reference to the following drawings in which like reference devices refer to like parts thereof throughout the various views and diagrams and in which;
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective illustration of a ring made according to the invention, showing approximately onehalf of the finger band, the remainder being shown in phantom form, and showing the setting portion and associated keying members or elements therein in solid line;
FIG. 2 is a section along the line 2-2 of FIG. 1, and,
FIG. 3 is a cut away perspective illustration of a further embodiment of the invention,
FIG. 4 is a schematic perspective illustration of a group of waxes prior to investment;
FIG. 5 is an enlarged perspective illustration of one of the waxes as shown grouped together in FIG. 4;
FIG. 6 is a schematic sectional illustration through an investment flask containing the waxes shown in FIG. ll, embedded within the investment material;
FIG. 7 is a schematic illustration showing the step of subjecting the flask to low tempterature heating;
FIG. 8 is a schematic illustration showing the step of subjecting the flask to immersion in a solvent solution;
FIG. 9 is a schematic illustration showing the step of subjecting the flask to moderate heating in an oven, and,
FIG. 10 is a schematic illustration showing the casting steps.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Before describing the actual steps of the method acinvention can be applied to jewellery such as rings,
brooches, earrings, necklaces and many other jewellery items in which it is desired to construct a jewel setting or decoration pieces as one part, and the remainder of the piece of jewellery as another part. It will also of course be understood that the method according to the invention is equally applicable to the use of two dif-' ferent precious metals, or to the use of the same precious metal, i.e. gold, in two colours for the two separate parts or to the use of the same precious metal in the same colour for both parts, although the latter instance would generally speaking be a somewhat unusual use of the invention unless there was a requirement for pre-polishing of the first part. The invention is therefore not to be confined simply to the casting of two different types of metal or to the casting of two different colours of the same metal. However, for the sake of simplicity in the following description, reference is made throughout to the use of a white gold jewel setting and a yellow gold band, while the entire process is referred to generically as bimetallic casting whether or not two different metals, or two different coloured pieces of the same type of metal or in fact two I different pieces of the same colour and carat of the same metal are used.
With reference now to FIGS. 1, 2 and 3,'it will be seen that this jewellery product produced according to the invention comprises a typical finger ring having a finger band portion 10 formed of yellow gold or the like, and a jewel setting portion indicated by the general reference arrow 11 extending therefrom. In this preferred embodiment of the invention, the jewel setting portion 11 is formed of white gold, and is cast, by the lost wax method, separately, in a preliminary stage. Accordingly, the jewel setting portion 11 of the embodiment shown in FIG. 1, is provided with jewel support members 12 of essentially standard design, and a setting stem member 13 extending downwardly into the yellow gold band 10.
In order to secure and hold the stem 13 in position, the stem 13 is provided on either side thereof with adjacent keying elements consisting of the blade-like members 14, cast integrally therewith of the same material (i.e'., the white gold) as the stem 13 and the jewel support members 12. The blade-like members 14 may be very short, or may extend partially around the yellow gold finger ring portion 10, or all the way around as shown in FIG. 1. It is desirable though not essential that the blade-like members 14 should incorporate one or more keying openings 15 extending therethrough, through which during the practice of the method according to the invention the yellow gold of the finger ring 10 may flow when in its molten state. In addition, in this particular design of ring, although without any limitation on the invention as such, the blade-like keying elements 14 are provided with subsidiary jewel mount plates 16 having jewel support fingers l7 thereon, the mounts 16 being arranged and located to lie on the outer surface of the yellow gold band 10. In addition, in this particular design of ring, although without any limitation to the invention, the keying elements-l4 may be further provided with the decorative ridge members 18 again adapted to lie in the surface of the yellow gold band 10, and add to the visual appeal of the ring.
It will be noted that in this embodiment of jewellery product, the jewel mounting member generally indicated as 11 is provided with keying elements 14 of the type which are embedded entirely within the yellow gold band 10, and in fact portions of the yellow gold band will actually flow through the keying openings 15, so as to effectively completely secure the mounting portion 11 in position, without the use of adhesives, brazing, welding, or the use of hard solder or the like, the jewel mounting portion 11 merely being held in position solely by the flowing of the yellow gold band 10 around the keying elements 14, and through the keying openings 15 therein, during manufacture.
According to a further embodiment, provision may be made for a still further and more complex design of ring, such as a mans signet ring or the like, in which white and yellow gold portions are given the appearance of actually having been interwoven or interleaved one with the other. This embodiment is shown in FIG. 3, in which the yellow gold band portion indicated as is only partially shown, the remainder having been cut away for the sake of clarity. It will be noted that in this embodiment, the white gold portions of the ring comprise essentially the lengthwise or longitudinal bands or strips indicated as 21, and the yellow gold portions, consist of the band 20, and the transverse strips 22. Preferably, longitudinal strips 21 are provided at appropriate positions, with keying openings indicated as 23 therethrough through which the yellow gold forming the band 20, and the transverse strips 22 may flow, thereby fastening and keying the white gold strips to the yellow gold. Obviously, such openings 23 must be located in positions where they are in the first place in contact with a portion of yellow gold on both sides, that is to say above and below the white gold strip. Such locations will be seen to be as at the cut away portion in FIG. 3, and similar openings will be arranged along each side and each end of the pattern of white gold strips, wherever the end portion of a white gold strip is overlapped on both sides by yellow.
Obviously, keying devices or elements 14 can be provided, without arranging holes or openings 15 through the white gold portion at all, the keying elements 14 being sufficiently securely held in position by the yellow gold of the ring 10 therearound. Alternatively for example although not illustrated, the keying elements 14 of the white gold portion illustrated in FIG. 1 could in place of the openings 15, or in addition thereto, be provided with outwardly extending transverse bars or ridges, (not shown), so that the yellow gold would flow therearound and firmly grip the same. Similarly, in the embodiment of FIG. 3, the white gold strips 21 could be provided with downwardly dependant keying members with or without holes therethrough as in FIG. 1, or with downwardly dependant keying members with or without bars or ridges extending transversely therefrom, although the provision of the holes 23 as shown in FIG. 3 is believed to be the most advantageous way of providing for keying of the parts together.
As stated, the present invention is concerned with the method for the production of the product shown in FIGS. 1 to 3, whether it be a finger ring, or any other jewellery item involving bimetallic casting as defined herein. In order to practice the method according to the invention, it is first of all necessary to make the first metallic part, usually the jewellery setting, by, eg., the lost wax method or die stamping or any other suitable technique. Thus a variety of jewellery settings may be made and stored, if desired.
WAX MODEL STAGE When it is then desired to manufacture a bimetallic lo jewellery item, such as the finger ring shown in FIGS. 1
to 3, the jewellery setting shown as 11, according to the first step of the invention, is embedded in a wax model of the second metallic part, usually the ring portion referenced as 10 in FIG. 1. As shown in FIG. 5, the resultant product is a composite of a metal setting 11 and a wax ring or band portion shown as 30 and a stemlike portion or gate 31. The production of such a combined metal setting and wax band may be prepared according to well known techniques for the production of waxes" employing rubber moulds, and, according to well known techniques. The stems or gates" 31 are then fastened to a circular ring member 32, so that they are then formed into a group with 30 to 50 such waxes" attached to one such ring 32.
INVESTMENT STAGE The next stage of the invention is the investment stage shown in FIG. 6. In this stage, the ring 32 and waxes 31 are supported on a rubber base 33 formed in a predetermined shape with a well 34 in the centre and a circular perimeter wall 35 around the edge. A steel or aluminum flask 36 is placed on the rubber base 33, fitting within the perimeter wall 35 as shown, and liquid investment 37 is poured into the flask 36 surrounding and investing the waxes 30 and the stems 31, and partially investing the ring member 32. The flask 36 containing the liquid investment is then subjected to a moderate vacuum, and preferably to moderate vibration, to remove all trapped air bubbles, according to well-know practice. Alternatively it is permissible to employ machines, known per se, which both mix and pour the investment under vacuum, or any other means for avoiding the presence of air bubbles. After the investment 37 has set hard, the rubber base 33 is removed, and usually the wax ring 32 is also removed thereby exposing the ends of the individual stems or gates 31.
The investment 37 may be plaster of paris or any other specially prepared investment powder material, details of which are well known in the jewellery manufacturing trade and require no further description.
WAX MELTING STAGE I The next stage of the method according to the invention is the stage in which the wax is removed. In the past, it has always been the practice to remove the wax by subjecting the flask and investment 37 to an extended period of heating at a very high temperature, in the region of I,300 to I,400 P, which melts out most of the wax and converts the remainder to carbon which is burned up at these temperatures. If these very high temperatures were not used, deposits of carbon tended to remain in the cavities within the investment, and were fatal to the satisfactory casting of metal.
In the past, any attempts to employ some form of bimetallic casting system in which a jewellery setting or the like already formed of gold or other metal was actually incorporated and embedded in the investment, was found to be completely impossible due to the fact that at these temperatures, in excess of 1,300 F, the gold or other precious metal was adversely affected. In particular, the finish on such gold or other precious metal was completely ruined when the same was subjected to these temperatures. Atempts to overcome this problem invariably met with failure, and in fact bimetallic casting in these types of metals has always been regarded as impossible.
By contrast however, it has been found that according to the practice of the method of the present invention, it is possible to remove all of the wax including the residual wax, without the formation of carbon deposits 'which were created in prior art high temperature procedures by means of removal of the wax under a relatively low temperature heating cycle preferably in the presence of steam and preferably at an elevated pressure followed by solvent washing of the flask, and cavities formed therein. Thus according to the practice of the invention, the flask and investment 37 are first of all subjected to relatively low temperature heating, by
placing the same within a steam pressure vessel 38 containing some water at room temperature which is then heated to generate steam until a pressure of between about 5 to 20 pounds per square inch is reached and maintaining this pressure. Generally a period of between about one to three hours is sufficient. These pressures will normally be reached at temperatures of between about 220 and 275 F. Preferably, according to the invention, the flask is placed with the wax stems 31 directed downwardly as shown in FIG. 7, to facilitate the downward flow of wax from the cavities within the investment 37, as the same is heated. Preferably the temperature and pressure will be within a narrower range of about 240 250 F at about 12 l5 p.s.i. and the time limit set between 1 and 1% hours. Longer periods of treatment at these temperatures and pressures has a tendency to mar the surface of the invest'm'ent and result in rougher castings.
Generally speaking the objective is to melt the wax gradually and cause it to flow out. Rapid heating has a tendency to boil the wax and damge the investment. Since the wax melts at about 160 F, the start up temperature should preferably be room temperature and the temperature is then brought up gradually. In fact, at the end of this stage the temperature can go as high as 600 to 650 F without damaging the first metal portions. In practice however such temperatures are unnecessary since the major portion of the wax will have been removed at the lower temperatures mentioned. While other heating mediums may possibly be suitable steam has the advantage of providing a moist atmosphere to facilitate flow of the wax and also is readily controlled to provide a gradual temperature build up. It has been found that by relatively low temperature or moderate heating in this manner, at an elevated pressure, almost all of the wax within the investment 37 can be removed, leaving only a fractional percentage remaining therein, usually in the form of a thin film, and without the formation of carbon.
SOLVENT WASHING STAGE The removal of any residual wax within the cavities formed in the investment 37 is preferably achieved by completely immersing the flask within a bath 39 containing a suitable solvent liquid. In the case of conventional wax such as so-called rubber base wax, a suitable solvent will be a strong commercial degreasing agent. Clorothene (Registered Trade Mark of Dow Chemical Company) has proved to be particularly suitable for the purpose. Preferably, the flask is placed therein with the cavities formed within the investment 37 directed upwardly so as to facilitate flow of the liquid solvent into the cavities without the formation of air pockets. After immersion for a suitable period of time anywhere from 5 minutes to an hour, the flask may be removed and shaken so as to remove all traces of liquid solvent therefrom, afterwhich it is found that the cavities formed within the investment 37 are completely free of any traces of wax or carbon which might impair the quality of the castings formed therein.
It will of course be understood that since the first metal part 11 remains trapped within the investment 37, notwithstanding removal of the wax therefrom, it is absolutely essential that both the heating step as described in relation to FIG. 7, and the solvent washing step as described in relation to FIG. 8, be carried out in such a manner that the first metal parts 11 are not disturbed, and that the surface finish on such metal parts is not in any way impaired and that they are not subjected to any temperatures which would come anywhere close to heating them to a plastic or molten state, or tarnish the finish thereon.
PREHEATING STAGE In accordance with conventional casting techniques as known in the art, it has been customary to cast the metal immediately after the burning out of the wax. At this stage the investment is still heated to a temperature of somewhere between l,0O0 and 1,400 F. Indeed, some authorities have recommended casting at even higher temperatures to ensure a greater fidelity of the finished casting to the original wax impression, and to avoid premature solidifying of the metal.
Thus, in conventional casting, after the investment has been thoroughly and completely and evenly heated in the burn out procedure, the flask is then removed and immediately placed in a suitable centrifugal casting machine (known per se) and the metal is cast with the investment at very high temperature.
By contrast however, according to the practice of the present invention, the investment 37 contains trapped within the' cavities therein, the first precious metal parts, which are liable to be damaged if they are heated to temperatures anywhere close to l,000 to l,400 F. The investment in fact will not usually reach a temperature much above 250 275 F, or in any event no higher than the temperature of the heating medium. In addition the solvent washing step cools the investment to much lower temperatures. Accordingly, the practice of the present invention provides a moderate casting pre-heating stage, restricted to temperatures of not more than between about 400 and 600 F, for a period of about 2 to 10 hours, so as to ensure that the investment 37 is completely evenly pre-heated throughout.
At these temperatures, the precious metal parts trapped in the investment 37 do not become damaged.
I However, according to the teaching of experts in this field which has been accepted for many years, restriction of the investment to such moderate temperatures prior to casting would result in substantial loss of detail and fidelity in the finished part. Suprisingly however, according to the practice of the present invention, it is found that these problems can be overcome during the casting procedure.
CASTING STAGE According to the practice of the present invention, the preheated flask 36 is fastened by any suitable clamping means in a centrifugal casting machine of any suitable type (the details of which are not shown) having a holder 41 which is mounted on a pivot axis 42 so as to permit the same to be rotated at high speeds to create the centrifugal force required. A crucible indicated schematically as 43 located within the holder 41 contains the molten gold or other metal, and a closure plate 44 associated with the crucible 43 closes the bottom end of the flask 36. In order to withdraw air from the bottom end of the flask 36, a vacuum tube 45 passes through the closure plate 44, being connected with any suitable vacuum source (not shown).
Further evacuation of any residual air within the cavities in the investment is achieved by placing a vacuum manifold 46 at the upper end of the flask 36, ie. the end remote from the cavities formed by waxes 30 and stems 31. During pouring of the molten metal into the lower end of the flask 36, the manifold 46 is subjected to continuous evacuation through any suitable vacuum tube 47, and, since the investment 37 therein will tend to be evacuated, especially at the time when molten metal is entering such cavities.
In order that the vacuum tubes 45 and 47 may rotate with the holder 41 they are provided with rotatable couplings (of any suitable conventional design) arranged on the axis of rotation 42 of the holder 41.
Just prior to the tipping of the crucible air is evacuated at both ends of the flask ie. by tube 45 at the lower end and by tube 47 and manifold 46 at the upper end. At the moment when the crucible is tipped evacuation through tube 45 is terminated to avoid any interference with flow of metal into the cavities, but evacuation through manifold 46 and tube 47 is continued until casting is completed.
Since the closure member 43 closes the lower end of the flask 36, and the vacuum tube 47 continues evacuation of air from the upper end of the flask 36, this has the effect of drawing the metal into the cavities thereby increasing the rapidity flow of the molten metal therein while at the same time any entry of any additional air into the lower end of the flask 36, in response to the evacuation of air through the vacuum manifold 46, is prevented by closure 43.
Other forms of vacuum application may also be suitable. Thus the invention does not exclude the use of a so-called vacuum furnace wherein the entire casting procedure is carried on in a vacuum.
Castings formed in this way are found to exhibit excellent fidelity to the contours of the cavities, notwithstanding the relatively low temperatures of the investment material during casting.
CLEANING STAGE After cooling the investment is broken and removed and the castings are cleaned ofi in a pickling solution and by steaming. The surface finish can be restored by coating the castings in boracic acid, annealing them at l,300 F for 15 to 30 seconds and removing the boracic acid with sulphuric acid. The casting is then rinsed in sodium cianide solution.
By the practice of the invention, it is found that pieces of jewellery such as finger rings and the like can be manufactured in two stages as described above, and in two different metals, or in two different colours of the same metal or indeed in two separate pieces of the same metal without any loss of finish whatever on the first metal part which is embedded in the investment during the casting of the second part, and the casting of the second part is completely effective to envelop and embed the hidded portions of the first part within it and make a perfect joint therewith without the use of any other means such as a solder or the like. In addition, by virtue of the practice of the present invention pieces of jewellery can be made in designs which were absolutely impossible under previously known techniques. Interlocking or interwoven designs such as that shown in FIG. 3 can be achieved quite readily at minimum expense, in such a manner that the two different metallic portions appear to be interwoven with one another in a manner which would be substantially impossible according to previous techniques.
Reference has been made throughout to wax and investment material. Obviously any other materials suitable for the purpose may be employed from time to time as circumstances permit.
The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features described, but comprehends all such variations thereof as come within the scope of the appended claims.
What I claim is:
l. The method of manufacturing an article of jewellery or the like constructed of two separate metal parts, and comprising;
manufacturing a first metal part of said article, said first metal part defining a visible portion of said article and a portion which will be hidden in said article;
embedding said hidden portion of said first metal part in a model of a second said metal part of said article leaving said visible portion exposed, said model being formed of disposable material which may be disposed of by the application of heat and a solvent;
investing said composite first metal part, and model of said second metal part in investment material, and permitting the same to harden;
subjecting said investment material to a melting heating step by heating the same to a temperature in the range of between and 650 F for a period sufficient to melt substantially all of said disposable material of said model of said second part therein, and permitting the same to run out of said investment, to leave a cavity therein defining the shape of said second metal part, and leaving the visible portion of said first metal part embedded within said investment and said hidden portion exposed within said cavity; subjecting said investment to the action of a solvent for said disposable material thereby to dissolve and remove any residual film thereof within said caviy;
subjecting said investment and first metal part therein to a casting pre-heating step by heating the same to a moderate temperature sufficient to evenly preheat said investment throughout to the same temperature without damage to said first metal part therein said temperature being not more than about 400 to 600 F;
casting said second metal part by introducing said second metal in a molten state into said cavity in said investment, said second metal enveloping said hidden portion of said first metal part and setting therearound, to form said particle, and,
removing said article from said investment material.
2. The method as claimed in claim 1 including the step of subjecting said investment material to a moderate vacuum, and moderate vibration, prior to hardening thereof.
3. The method as claimed in claim 1 wherein said melting heating step is carried out by subjecting said investment material to a temperature in the region of between about 220 and 275 F, in the presence of steam, with said investment material oriented and supported so as to permit said disposable material therein to melt, and flow outwardly from said investment under the influence of gravity.
4. The method as claimed in claim 1 wherein said melting heating step is carried out by enclosing said investment material within a pressure vessel containing water at or about room temperature and heating said pressure vessel until it reaches a pressure of between about 12 and 15 pounds per square inch, at a temperature of between about 240 and 250 F, over a period of between about 1 and 1% hours, with said investment material oriented and supported within said pressure vessel and subject to the progressive heating action of steam therein thus causing said disposable material to melt and flow freely therefrom under the influence of gravity.
5. The method as claimed in claim 1 wherein said cleaning step comprises immersing said investment in a liquid solvent for said disposable material, said solvent flowing into said cavity and dissolving any residual said between about 2 to 10 hours.
7. The method as claimed in claim 1 including the step of subjecting said investment to a moderate vacuum, during casting, whereby to assist flow of said molten second metal into said cavity.
8. The method as claimed in claim 1, wherein said investment material is contained within a flask having upper and lower ends, and including the step of closing both said ends of said flask prior to casting, and, just prior to casting, subjecting both ends of said flask to a moderate vacuum where y to extract an both from said cavities, and from the surrounding investment material, and terminating said vacuum at one said end of said flask and immediately introducing said second molten metal into said cavity from said last mentioned end of said flask, while continuing to subject said other end of said flask to said moderate vacuum.
9. A method as claimed in claim 1 wherein said melting heating step is carried out by enclosing said investment material within a pressure vessel containing water at or about room temperature and heating said pressure vessel until it reaches a pressure of between about 12 and 15 pounds per square inch at a temperature of between about 240 250 F over a period of between about 1 and l and hours, and wherein said preheating step is carried out at a temperature of between about 400 and 600 F for a period of from between about 2 to 10 hours, and wherein said investment material is contained within a flask having upper and lower ends, and including the step of closing both said ends of said flask prior to casting, and, just prior to casting, subjecting both ends of said flask to a moderate vacuum, whereby to extract air both from said cavities, and from the surrounding investment material, and terminating said vacuum at one said end of said flask and immediately introducing said second molten metal into said cavity from said last mentioned end of said flask, while continuing to subject said other end of said flask to a moderate vacuum whereby to continuously withdraw any residual air from said cavity through said investment, and thus facilitate filling of said cavity by said molten metal;